In the manufacture of articles from precipitation hardenable high strength aluminium alloys, the final thermo-mechanical treatment involves solution treatment of the alloy followed by quenching and then natural or artificial ageing. This process results in hardening of the alloy.
Prior to the final thermo-mechanical treatment, the alloy can be hot or cold worked in a number of different ways, for example rolling, extruding or forging. This stage in the preparation of a material is referred to as the intermediate thermo-mechanical treatment.
It is known to prepare composites comprising a particulate or short fibre ceramic reinforcement in a matrix comprising a precipitation hardenable aluminium alloy. The conventional treatments for such composites have followed the same procedure as for the unreinforced alloys, i.e. solution treating the material and then artificially or naturally ageing it to precipitate the strengthening phase. We have now found that introduction of an additional step between the intermediate and final thermo-mechanical treatments leads to a surprising improvement in the properties of such composites.